The present invention relates an exhaust manifold for an internal combustion engine, and more particularly to improvements in an exhaust manifold of collecting exhaust passages for straightly arranged cylinders into one passage.
Japanese Published Patent Application No. 10-317953 discloses an exhaust manifold applied to an exhaust system for one bank of a V-8 engine. The exhaust manifold comprises a straight collection pipe and four branch pipes connected to exhaust ports of cylinders. The four branch pipes are arranged in parallel and are connected to the collection pipe so that an upper periphery of each branch pipe is aligned with a tangent at a top of circular cross-section of the collection pipe. Further, each branch pipe is collected into the collection pipe at a confluence angle of 67.5° or less.